Method for creating a mediastinal working space

ABSTRACT

A mechanical lifting retractor is provided which increases working space in the chest for cardiac surgery by temporarily expanding the space between the rib cage and the pericardium. The lifting device has a pair of parallel right-angled retractors. Distal portions of the retractors are insertable in side-by-side parallel relation between a pair of adjacent ribs in the rib cage and into the mediastinal space between the ribs and sternum and the pericardium beneath them. The distal portions are pivotable into a lifting position in which they are separated by a rotational angle of approximately 180°. Following insertion of the distal portions into the mediastinal space, the distal portions are rotated into the lifting position and oriented in the sagittal plane such that each distal portion extends beneath one of the ribs. A lifting force is applied to the lifting retractor, causing the distal portions to engage the ribs and to lift the rib cage and thereby enlarging the mediastinal space. The lifting force is maintained for the duration of the surgical procedure.

The present application is a continuation of application Ser. No.08/279,290, filed Jul. 22, 1994, now abandoned.

FIELD OF THE INVENTION

The present invention relates generally to the field of surgicalretraction devices and, particularly, to the field of devices foroptimizing working space in the chest for endoscopic cardiac surgery.

BACKGROUND OF THE INVENTION

Present techniques for providing surgical access to the heart andcoronary arteries are highly invasive. Cardiac surgery is conventionallyperformed via a median sternotomy, a procedure in which the patient'sskin is incised at the midline overlying the chest, and in which thesternum is divided longitudinally along its entire length. Access may begained to the coronary arteries for bypass surgery, or to the heartvalves for valve replacement, by forming an incision in the pericardium,the fibrous sac enclosing the heart. The cut edges of the sternum areretracted with metal retractors, exposing a large cavity to allowsurgery to be performed on the heart.

Access to the heart for certain procedures may be gained using asubxiphoid incision, which provides an entrance into the abdominalcavity, and by a second incision through the diaphragm and thepericardium to provide entry from the abdominal cavity to the inferioraspect of the heart. Implantable cardiac pacemakers can be implantedusing this approach. However, this technique does not provide sufficientexposure of the coronary arteries or heart valves to allow it to be usedfor coronary artery bypass surgery or cardiac valve replacement.

Some procedures may be performed using a suprasternal approach, duringwhich a rigid endoscope is inserted into the mediastinal cavity (thecavity which contains the heart and the other organs positioned betweenthe pleural sacs) through a small incision formed above the sternum.However, this technique is useful for a limited number of procedures,such as visualization of the mediastinal cavity (mediastinoscopy), andsmall procedures such as lymph node biopsy.

Access to the anterior extrapericardial space for closed cardiac massagein cardiac arrest may be gained using an intercostal approach. For thisapproach, an incision is formed in the space between the ribs adjacentthe sternum. An inflatable ring is inserted through the incision andplaced over the heart. The ring is inflated to compress the heart and tothereby circulate blood during cardiac arrest. Because the heart liesjust beneath the sternum, very little working space exists formanipulation of the inflatable ring or for insertion of surgicalinstruments between the heart and the sternum and adjacent fibs.

Thoracoscopic techniques may allow access to the heart from a lateralapproach, through the pleural cavity. Multiple incisions are formed inintercostal sites on one side of the chest. The lung on that side of thechest is collapsed, and the pleura is incised to give access to theheart in the mediastinum. Disadvantages of this approach include theincreased instrument length required to reach the heart, and the lack ofaccess to the anterior surface of the heart, which is covered by thesternum.

Since the subxiphoid, suprasternal, intercostal and thoracoscopicapproaches provide limited access to the heart, researchers arepresently considering endovascular substitutes for open heart surgery.For example, some researchers have reported animal studies in which atotal endovascular approach was used to implant heart valves inpiecemeal fashion in animals and to assemble the valves in situ. Thisapproach has inherent technical difficulties; for example, thedevelopment of reliable valves capable of being assembled in situ. Evensome conventional heart valves designed for open heart placement sufferfrom fatigue fracture problems.

SUMMARY OF THE INVENTION

The method and apparatus of the present invention utilize mechanicallifting of the rib cage to create a working cavity above the heart, sothat cardiac surgery may be performed through a number of smallincisions in the thoracic cavity. Use of this procedure eliminates theneed for forming a large incision in the chest and for dividing thesternum.

A specialized retractor is inserted through an incision formed in thechest and is passed between a pair of ribs into the intercostal spaceoverlying the heart. The preferred retractor has two retractor barswhich are independently rotatable between an insertion position and alifting position. In the insertion position, the retractor bars arepositioned in close parallel relationship to enable their simultaneousinsertion through the incision. Once the retractor bars are within theintercostal space, each is rotated through a rotational angle ofapproximately 90° in a direction opposite from the direction of rotationof the other retractor bar. The retractor bars are aligned in thesagittal plane, such that each bar contacts one of the ribs. Theretractor bars are locked into the open position and the retractor islifted by a powered lifting device, or it is lifted by hand and securedin an elevated position by means of a suspension system secured to theside rail of the operating table supporting the patient.

Alternative retractors include a single legged retractor or a fanretractor that opens to an acute angle. The retractors of the presentinvention are suitable for introduction through subxiphoid,suprasternal, or intercostal incisions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of an intercostalretractor according to the present invention, showing the retractor barsin the insertion position.

FIG. 2 is a side view of the intercostal retractor of FIG. 1.

FIG. 3 is a front view of the intercostal retractor of FIG. 1.

FIG. 4 is a side view of the intercostal retractor of FIG. 1, showingthe retractor bars in the lifting position.

FIG. 5 is a front view of the intercostal retractor of FIG. 1, showingthe retractor bars in the lifting position.

FIG. 6 is a perspective view of the intercostal retractor of FIG. 1,showing the retractor bars in the lifting position.

FIG. 7 is a cross-sectional view of the thoracic cavity,diagrammatically showing insertion of the retractor bars of the FIG. 1retractor between a pair of ribs into the intercostal space.

FIG. 8 is a cross-sectional view similar to FIG. 7, showing theretractor positioned in the sagittal plane, further showing theretractor bars each engaged with one of the fibs, and further showingapplication of a lifting force to the retractor by a mechanical liftingarm.

FIG. 9 is a cross-sectional view similar to FIG. 8, further showinginsertion of surgical instruments through auxiliary incisions, andfurther showing dissection of the pericardium to expose the heart.

FIG. 10 is a cross-sectional view similar to FIG. 9, further showinginsertion of an endoscope through an auxiliary incision and showing thepericardium dissected to expose the heart and coronary artery, andfurther showing the internal mammary artery dissected to form a bypassgraft.

FIG. 11 is a perspective view of a second embodiment of a liftingretractor according to the present invention.

FIG. 12 is a perspective view of a third embodiment of a liftingretractor according to the present invention.

FIG. 13 is a cross-sectional view of the thoracic cavity,diagrammatically showing insertion of the FIG. 12 retractor through asuprasternal incision.

FIG. 14 is a cross-sectional view of the thoracic cavity,diagrammatically showing insertion of the FIG. 12 retractor through asubxiphoid incision and further through an incision in the diaphragm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The retractor of the present invention is configured to engage with aportion of a patient's fib cage (i.e. with the sternum and/or one ormore of the ribs) and to impart lifting force to the fib cage. In thismanner, the intercostal space is used to create a working space betweenthe heart and the rib cage by enlarging the mediastinal space (the spacebetween the rib cage and pericardium), allowing visualization of theheart using an endoscope and further allowing manipulation ofendoscopically placed surgical instruments.

Referring to FIGS. 1-6, a preferred intercostal retractor 10 iscomprised of a lifting body 12, a pair of retractor arms 14a, 14b and amounting device 16 for mounting the intercostal retractor 10 to amechanical lifting arm, such as the one described in application Ser.No. 07/959,717, now abandoned, which is incorporated herein byreference.

The lifting body 12 is rectangular and has a superior face 18 and aninferior face 20. A pair of parallel throughbores 22a, 22b (FIG. 1)extend through the body 12 from the superior face 18 to the inferiorface 20. The mounting device 16, which is preferably a dovetailconnector configured to mate with a dovetail mount on the mechanicallifting arm (not shown), is attached to a side face 17 of the liftingbody 12.

A position stop 26 is secured to the superior face 18 of the liftingblock 12, adjacent to the throughbores 22a, 22b. This stop is preferablyan elongate rectangular bar having an edge 33 (shown in FIG. 2)immediately adjacent to the throughbores 22a, 22b. A recessed lockinggroove 24 is formed into the superior face 18 of the lifting body 12. Asshown in FIGS. 1 and 6, the locking groove 24 is semi-circular in shape,having an open side defined by a straight edge 25 centered along theside wall 17 of the lifting body 12 and an arcuate upstanding sidedefined by an edge 27 extending towards the position stop 26.

The retractor arms 14a, 14b have intermediate portions 28a, 28bpartially disposed within the respective throughbores 22a, 22b of thelifting body 12. Proximal ends 29a, 29b, respectively, of intermediateportions 28a, 28b are contiguous with deployment bars 30a, 30b, atelbows 35a, 35b as shown in FIGS. 1 and 6. Tips 31a, 31b are located atthe distalmost ends of the deployment bars 30a, 30b.

Retractor bars 32a, 32b are contiguous with and extend laterally fromthe intermediate portions 28a, 28b at the distal ends of the retractorarms 14a, 14b. When the device is positioned with the retractor arms14a, 14b oriented vertically as shown in FIG. 1, each deployment bar30a, 30b and the proximal end 29a, 29b of its respective retractor arm14a, 14b lies in a vertical plane that is perpendicular to the verticalplane of its corresponding retractor bar 32a, 32b. The retractor bars32a, 32b are preferably 2-3 cm in length.

The intermediate portions 28a, 28b are slidably and rotatably disposedwithin the throughbores 22a, 22b, respectively, such that rotation ofthe deployment bars 30a, 30b produces corresponding rotation of theretractor bars 32a, 32b. In this manner the retractor arms 14a, 14b aremovable between an insertion position, shown in FIGS. 1-3, and a liftingposition shown in FIGS. 4-6. In the insertion position, the retractorbars 32a, 32b are disposed in closely spaced generally parallelrelationship, while and the deployment bars 30a, 30b are separated by arotational angle of approximately 180°. In the lifting position thedeployment bars 30a, 30b are in close parallel relationship and theretractor bars 32a, 32b are separated by an angle of approximately 180°.

As best shown in FIG. 6, the tips 31a, 31b slip into the locking groove24 when the retractor arms 14a, 14b are moved into the lifting position.This provides resistance against rotational movement of the retractorarms 14a, 14b which might otherwise be caused by torsional forcesreceived by the retractor arms 14a, 14b during lifting.

The position stop 26 helps to ensure that the retractor bars 32a, 32bare aligned with each other as they are inserted into the intercostalspace. Alignment of the retractor bars 32a, 32b helps to reduce thelikelihood that the retractor bars will snag tissue surrounding orunderlying the incision during insertion. When the retractor arms 14a,14b are in the insertion position, the tips 31a, 31b of the deploymentbars 30a, 30b abut the position stop 26 as shown in FIGS. 1 and 2.During insertion of the retractor bars 32a, 32b through an incision, theuser may hold the tips 31, 31b against the position stop 26 (such as byapplying thumb pressure) to ensure that the retractor bars 32a, 32bremain in side-by-side relationship.

Use of the intercostal retractor of the present invention will next bedescribed with reference to the representations of a thoracic cavityshown in FIGS. 7-10. These show a patient's sternum AA, ribs BB, spineEE, xiphoid process FF, and diaphragm GG. The heart is shown in FIGS. 9and 10 and is designated HH; the pericardium, which encases the bean, isdesignated II. Intercostal space LL lies between the pericardium II andthe sternum AA.

For intercostal lifting, a small incision JJ (FIG. 7) of approximately1-2 cm in length is made through the skin and tissue overlying the ribsBB. The incision JJ is preferably formed in a location that will enableinsertion of the retractor bars 32a, 32b into the mediastinal space LLoverlying the heart (through approximately the third intercostal space).An incision formed approximately 1 cm lateral to the sternum is suitablefor this purpose. The deployment bars 30a, 30b of the retractor arms14a, 14b are moved against the position stop 26 (best shown in FIGS.1-2) to place the retractor bars 32a, 32b, in the insertion position(i.e. such that the retractor bars 32a, 32b, are close together andapproximately parallel with each other). The retractor bars 32a, 32b areinserted through the incision JJ between a pair of adjacent ribs, whichare specifically designated CC, and DD. A hooking motion, as depicted inFIG. 7, is used for insertion of the retractor bars 32a, 32b so that theretractor bars pass between the ribs CC, DD and into the space LL lyingbeneath the ribs CC, DD.

The deployment bars 30a, 30b of the retractor arms 14a, 14b are nextrotated into the lifting position to rotate the retractor bars 32a, 32bsuch that they are separated by a rotational angle of 180°. The liftingbody 12 is next rotated about its longitudinal axis through an angle ofapproximately 90° to align the retractor bars 32a, 32b in the sagittalplane, such that one bar contacts the superior rib (rib DD) and theother bar contacts the inferior rib (rib CC) as shown in FIG. 8.

The dovetail connector 16 on the lifting body 12 is next connected to amechanical lifting arm (designated 200 in FIG. 8) and a lifting force isapplied in a direction substantially normal to plane of the ribs CC, DDas indicated by the arrow in FIG. 8. The retractor 10 may alternativelybe lifted by hand and secured in an elevated position by means of asuspension system secured to a side rail of an operating table whichsupports the patient.

As can be seen in FIG. 8 the ribs are lifted to increase the width w ofthe mediastinal space LL so as to increase the working space between thepericardium II and the ribs BB and sternum AA.

Referring to FIG. 9, an endoscope 202 and surgical instruments, such asthe curved scissors designated 204, may be inserted through additionalsmall intercostal incisions KK. Instruments may alternatively beinserted through the same incision JJ through which the retractor bars32a, 32b are inserted. Surgical access to the heart HH and coronaryartery NN is gained by incising the pericardium II using the curvedscissors 204.

During placement of an implantable cardiac pacemaker via a subxiphoidincision, an intercostal retractor according to the present inventionmay be used to lift the sternum AA and rib cage to expose the diaphragmand to provide a surgical approach through the diaphragm GG to the heartvia a subxiphoid incision.

Referring to FIG. 10, the intercostal retraction technique justdescribed is also useful for providing access to the internal mammaryartery, which is used to bypass stenotic segments of the coronary arteryduring coronary artery bypass surgery. The internal mammary artery(designated MM in FIG. 10) extends behind the cartilages of the firstsix ribs BB, about 1.25 cm from the lateral border of the sternum AA.

To dissect the internal mammary artery MM, the intercostal retractor 10is oriented as described above, and is positioned adjacent the sternumAA at a location that is approximately 2 cm lateral to the sternalborder. Dissection instruments such as right angled clamps, curvedscissors and an electrocautery probe (all not shown) may be introducedvia the retractor incision site JJ or through ancillary intercostalports KK.

An endoscope 202 (preferably one providing visualization at an angle ofapproximately 30°-45°) is inserted through an ancillary intercostal portKK to allow visualization of the region of the internal mammary arteryMM. The pleura and the fascial layer (both not shown) coveting theartery are incised on either side of the internal mammary artery MM, anda pedicle (not shown) containing the internal mammary artery isdissected. To create a bypass graft, side branches (such as thosedesignated OO and PP) of the internal mammary artery MM are individuallyclipped using a pair of spaced apart metal vascular clips 206 per sidebranch, and each side branch is transected between its respective clips.Dissection is carried out in this manner until a segment of the internalmammary artery MM is dissected that is of sufficient length for a bypassgraft.

Next, distal end QQ of the internal mammary artery MM is clipped andtransected. Vascular clips 206 on the side branches OO, PP may bereplaced with suture ties (not shown) for increased occlusive stability.The pericardium II is next incised as described above to expose thecoronary artery, designated NN in FIG. 10. Finally, the internal mammaryartery MM is anastomosed to the coronary artery NN to bypass thestenotic segment or segments of the coronary artery NN.

A second embodiment 210 of a mediastinal retractor according to thepresent invention is shown in FIG. 11. The second embodiment 210 iscomprised generally of a lifting body 212, retractor arms 214a, 214b,and actuator levers 230a, 230b which rotate the retractor arms 214a,214b. The retractor arms 214a, 214b are comprised of intermediateportions 228a, 228b and retractor bars 232a, 232b which extend laterallyfrom their respective intermediate portions 228a, 228b.

As with the first embodiment, the retractor arms 214a, 214b of thesecond embodiment are rotatable between an insertion position and alifting position. In the insertion position (which is similar to theposition of the retractor arms 14a, 14b of the first embodiment 10 shownin FIG. 1), the retractor bars 232a, 232b are positioned in side-by-siderelationship for insertion through an incision. In the lifting position,shown in FIG. 11, the retractor bars 232a, 232b are separated by arotational angle of preferably 180°.

The remaining features of the second embodiment will be brieflydescribed. Detailed descriptions of these features and theirconstruction may be found in U.S. patent application Ser. No.07/890,033, filed May 28, 1992, and U.S. patent application Ser. No.08/128,427, filed Sep. 28, 1993, which are hereby incorporated byreference.

Rotation of the retractor arms 214a, 214b between the lifting andinsertion positions is carried out through rotation of the actuatorlevers 230a, 230b. A locking mechanism 224 is provided which has a slot(not shown) which engages the actuator levers 230a, 230b when theretractor arms 214a, 214b are in the lifting position.

The retractor arms 214a, 214b are coupled to the lifting body 212, andthe lifting body 212 is rotatably disposed within a sleeve 211. Adovetail mount 216 is mounted to the sleeve 211. The lifting body 212 isrotatable within the sleeve 211 (around the common longitudinal axis ofthe sleeve 211 and the lifting body 212).

The lifting body 212 is spring mounted within the sleeve 211 and islongitudinally slidable within the sleeve 211 when a tensile load isapplied between the sleeve 211 and the retractor arms 214a, 214b. Keys225 formed on the lifting body 212 engage with splines 227 formed in thesleeve 211 when the lifting body 212 slides in the distal direction by apredetermined distance. A spring (not shown) inside the sleeve 211controls longitudinal sliding of the lifting body 212 so as to preventengagement of the keys 225 and splines 227 until the tensile load on theretractor arms 214a, 214b reaches a predetermined level. A lifting forceindicator 223 indicates the lifting force being applied during use.

The first and second embodiments are preferable because locking the arms14a, 14b (or, with respect to the second embodiment, the arms 214a,214b) with the retractor bars 32a, 32b (232a, 232b in the secondembodiment) spaced 180° minimizes the effects of torsion on the arms14a, 14b (214a, 214b) during lifting. However, alternative embodimentsmay be envisioned which employ a single legged retractor (e.g. a singleright-angle retractor similar to a single one of the arms 14a, 14b whichis passed between two ribs into the intercostal space and extendedbeneath the sternum) or a fan-type retractor having two arms that pivotto form an acute angle between them.

A third embodiment of a fan retractor 110, which may be used forsubxiphoid or suprasternal lifting, is shown in FIG. 12 and will bebriefly described. A detailed description of a fan retractor of thistype appears in U.S. patent application 07/890,033 filed May 28, 1992,and is hereby incorporated by reference.

The fan retractor 110 has a lifting body 112 having a pair ofthroughbores 122a, 122b symmetrically offset from the longitudinal axisof the lifting body 112. Retractor arms 114a, 114b are rotationallypositioned within the throughbores 122a, 122b.

The retractor arms 114a, 114b are comprised of intermediate portions128a, 128b, retractor bars 132a, 132b, and deployment paddles 130a,130b. The intermediate portions 128a, 128b are partially and rotatablydisposed within the throughbores 122a, 122b, respectively. Retractorbars 128a, 128b extend laterally from the distal ends of theintermediate portions 128a, 128b, and deployment paddles 130a, 130b areattached to the proximal ends of the intermediate portions 128a, 128b.

The retractor bars 132a, 132b are rotatable between an open (lifting)position, shown in FIG. 12, in which they are separated by an acuterotational angle, and a closed (insertion) position (shown in FIGS. 13and 14) in which the retractor bars 132a, 132b are positioned in closeparallel relationship to permit their simultaneous insertion through asmall (i.e. 1-2 cm) incision. Rotation of the retractor bars 132a, 132bis achieved by rotating the respective deployment paddles 130a, 130b asindicated by arrows in FIG. 12.

A dovetail connector 116 is preferably attached to the lifting body 112for connecting the lifting body to a mechanical lifting arm such as thelifting arm 200 shown in FIG. 7.

A subxiphoid or suprasternal retractor may alternatively be providedwith a single right angle retractor arm, such as the retractor arm 114a,fixed to the lifting body 112.

Referring to FIG. 13, to use the retractor of FIG. 12 for cardiacsurgery using a suprasternal approach, a suprasternal incision RR isformed in the skin and underlying tissue, which are together designatedVV. The retractor bars 132a, 132b are positioned in the closed positionas shown, and are passed through the incision RR and into themediastinal space LL, beneath the sternum AA. The retractor bars 132a,132b are next rotated into the open position (which is shown in FIG.12). The retractor 110 is lifted in the same manner shown in FIG. 8 withrespect to the intercostal retractor, causing the retractor bars 132a,132b to deliver a lifting force to the sternum AA. The retractor 110 ismounted via the dovetail mount 116 to a lifting device, such as themechanical lifting arm shown in FIG. 8, to maintain lifting throughoutthe duration of the procedure.

Use of the retractor of FIG. 12 using a subxiphoid approach isillustrated in FIG. 14. As there shown, the retractor bars 132a, 132b,which are initially in the insertion position, are passed through asubxiphoid incision SS formed in the skin and underlying tissue(collectively designated as UU) and subsequently through an opening TTformed in the diaphragm GG. The retractor bars 132a, 132b are nextrotated into the open, lifting position shown in FIG. 12.

The retractor 110 is next lifted in the manner illustrated with respectto the intercostal retractor (FIG. 8), thereby imparting a lifting forceto the sternum AA and ribs BB via the retractor bars 132a, 132b. Theretractor 110 is mounted via the dovetail mount 116 to a lifting device,such as the mechanical lifting arm shown in FIG. 8, to maintain liftingthroughout the duration of the procedure.

Because the third embodiment of a lifting retractor according to thepresent invention is designed to be inserted through a subxiphoid orsuprasternal incision and positioned in contact with the sternum or witha number of adjacent ribs lateral of the sternum, the retractor bars132a, 132b are preferably formed to have a greater length than theretractor bars 32a, 32b of the intercostal retractor. Retractor bars132a, 132b of the alternative lifting retractor are preferably 4-6inches in length.

Conclusion

While preferred embodiments of the invention have been illustrated anddescribed, it should be understood that the invention is not limited tothese embodiments, but rather is defined by the following claims.

What is claimed is:
 1. A method of elevating a rib cage having ribs anda sternum to create a working space beneath the sternum and rib cagewithout performing a sternotomy, said method comprising the steps of:(a)providing a retractor device having a first proximal portion and a firstretractor bar joined in angular relation; (b) forming a small incisionin tissue adjacent to the rib cage; (c) passing the first retractor barthrough the incision, between a pair of the ribs which adjoin thesternum at one side of the sternum, and into a space beneath the ribcage, leaving the first proximal portion partially extending between theribs and out of the space beneath the rib cage; (d) positioning thefirst retractor bar beneath one of the ribs and engaging the rib cagewith the retractor device; (e) applying a lifting force to the firstproximal portion of the retractor device to lift the rib cage and thesternum, thus creating a mediastinal working space within the rib cage;and (f) performing a surgical procedure within the mediastinal workingspace while maintaining the lifting force for the duration of thesurgery.
 2. The method of claim 1 wherein:step (a) provides a retractordevice having a lifting body, wherein the first proximal portion extendsfrom the lifting body and forms a first lifting arm with the firstretractor bar, and wherein the retractor device further includes asecond lifting arm having a second proximal portion extending from thelifting body and a second retractor bar extending in angular relation tothe second proximal portion, the first and second retractor barspivotable about the longitudinal axes of their respective proximalportions; and steps (c) and (d) include the steps of(i) pivoting thefirst and second retractor bars into an insertion position wherein thefirst and second retractor bars are in close generally parallelrelationship; (ii) simultaneously passing the first and second retractorbars through the incision, between a pair of the ribs adjoining thesternum, and into a position wherein the first and second retractor barsare beneath the rib cage and their proximal portions extend between theribs; and (iii) after step (ii), pivoting the first and second retractorbars into a lifting position wherein the first and second retractor barsare separated by a rotational angle and wherein each of the first andsecond retractor bars is positioned to engage one of the ribs uponapplication of the lifting force.
 3. The method of claim 2 wherein step(iii) includes the step of pivoting the first and second retractor barsto a lifting position wherein the first and second retractor bars extendsubstantially longitudinally of one another.
 4. The method of claim 1wherein:step (a) provides a retractor device having a lifting body,wherein the first proximal portion extends from the lifting body and isjoined in angular relation to the first distal portion to form a firstlifting arm with the first distal portion, and wherein the retractordevice further includes a second lifting arm having a second proximalportion extending from the lifting body and a second distal portionextending in angular relation to the second proximal portion, the firstand second distal portions pivotable about the longitudinal axes oftheir respective proximal portions; and steps (c) and (d) include thesteps of(i) pivoting the first and second distal portions into aninsertion position wherein the first and second distal portions are inclose generally parallel relationship; (ii) simultaneously passing thefirst and second distal portions through the incision, between a pair ofthe ribs adjoining the sternum, and into a position wherein the firstand second distal portions are beneath the rib cage and their proximalportions extend between the ribs; and (iii) after step (ii), pivotingthe first and second distal portions into a lifting position wherein thefirst and second distal portions are separated by a rotational angle andwherein each of the first and second distal portions is positioned toengage one of the ribs upon application of the lifting force.
 5. Themethod of claim 1 wherein:step (a) provides a retractor device having alifting body, wherein the first proximal portion extends from thelifting body and is joined in angular relation to the first distalportion to form a first lifting arm with the first distal portion, andwherein the retractor device further includes a second lifting armhaving a second proximal portion extending from the lifting body and asecond distal portion extending in angular relation to the secondproximal portion, the first and second distal portions pivotable aboutthe longitudinal axes of their respective proximal portions; and steps(c) and (d) include the steps of(i) pivoting the first and second distalportions into an insertion position wherein the first and second distalportions are in close generally parallel relationship; (ii)simultaneously passing the first and second distal portions through thefirst incision, through the second incision, between a pair of the ribsadjoining the sternum, and into a position wherein the first and seconddistal portions are beneath the rib cage and their proximal portionsextend between the ribs; and (iii) after step (ii), pivoting the firstand second distal portions into a lifting position wherein the first andsecond distal portions are separated by a rotational angle and whereineach of the first and second distal portions is positioned to engage oneof the ribs upon application of the lifting force.
 6. A method ofelevating a rib cage having ribs and a sternum to create a working spacebeneath the sternum and rib cage without performing a sternotomy, saidmethod comprising the steps of:(a) providing a retractor device having adistal portion and a proximal portion joined in angular relation; (b)forming a small incision in tissue adjacent to the rib cage; (c) passingthe distal portion of the retractor device through the incision, betweena pair of the ribs which adjoin the sternum at one side of the sternum,and into a space beneath the rib cage, leaving the proximal portionpartially extending between the ribs and out of the space beneath therib cage, and (d) positioning the distal portion beneath one of the ribsand engaging the rib cage with the retractor device; (e) applying alifting force to the proximal portion of the retractor device to liftthe rib cage and the sternum, thus creating a mediastinal working spacewithin the rib cage; (f) while maintaining the lifting force, performinga surgical procedure utilizing surgical instruments introduced into themediastinal working space between a pair of the ribs which adjoin thesternum at one side of the sternum.
 7. A method of elevating a rib cagehaving ribs and a sternum to create a working space beneath the sternumand rib cage without performing a sternotomy, said method comprising thesteps of:(a) providing a retractor device having a lifting body, a firstlifting arm having a proximal portion extending from the lifting bodyand a first retractor bar extending in angular relation to the proximalportion, and a second lifting arm having a proximal portion extendingfrom the lifting body and a second retractor bar extending in angularrelation to the proximal portion, the first and second retractor barspivotable about the longitudinal axes of their respective proximalportions; (b) forming a small incision in tissue adjacent to the ribcage; (c) pivoting the first and second retractor bars into an insertionposition wherein the first and second retractor bars are in closegenerally parallel relationship; (d) simultaneously passing the firstand second retractor bars through the incision, between a pair of theribs which adjoin the sternum at one side of the sternum, and into aposition wherein the first and second retractor bars are beneath the ribcage and their proximal portions extend between the ribs; and (e) afterstep (d), pivoting the first and second retractor bars into a liftingposition wherein the first and second retractor bars are separated by arotational angle and wherein each of the first and second retractor barsis positioned to engage one of the ribs upon application of the liftingforce; (f) applying a lifting force to the proximal portion of theretractor device to lift the rib cage and the sternum, thus creating amediastinal working space within the rib cage; (g) while maintaining thelifting force, performing a surgical procedure utilizing surgicalinstruments introduced into the mediastinal working space between a pairof the ribs which adjoin the sternum at one side of the sternum.
 8. Themethod of claim 7 further comprising the step of locking the retractorarms in the lifting position prior to application of the lifting force.